/* Create classes from their modules and names. * * Copyright: Copyright (C) D Language Foundation 2023 * License:   $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0) * Authors:   Walter Bright, Steven Schveighoffer * Source:    $(DRUNTIMESRC core/_factory.d) */ module core.factory; /** * Create instance of class specified by the module symbol and a string * representing the name of the class. * The class must either have no constructors or have * a default constructor. * Params: *   mod = symbol representing the module that the class is in *   classname = string representing the name of the class * Returns: *   null if failed * Example: * --- * module foo.bar; * * class C * { *     this() { x = 10; } *     int x; * } * * void main() * { *     auto c = cast(C)factory!(foo.bar)("C"); *     assert(c !is null && c.x == 10); * } * --- */Object factory(alias mod)(string classname){    foreach(cl; _getModuleClasses!mod)    {        if (cl.stringof == classname)            return cl.classinfo.create();    }    return null;} @system unittest{    Object valid_obj = factory!object("Object");    Object invalid_obj = factory!object("__this_class_doesnt_exist__");     assert(valid_obj !is null);    assert(invalid_obj is null);} /************************************** * Retrieve as a tuple all the types of the top level classes in the module mod. */private template _getModuleClasses(alias mod) {   alias result = _AliasSeq!();   static foreach(m; __traits(allMembers, mod))      static if(is(__traits(getMember, mod, m) == class))         result = _AliasSeq!(result, __traits(getMember, mod, m));   alias _getModuleClasses = result;} private template _AliasSeq(TList...) { alias _AliasSeq = TList; }